Flying saucers (aka dead pixels)

In footage posted to YouTube Aug. 18, user "StephenHannardADGUK" applies a series of filters to a Curiosity image of the nearby rim of Gale crater, revealing what he says are four flying saucer-like objects stationed in the sky. More than 700,000 people have since given the video a gander.

"Four objects caught by Mars Curiosity, very difficult to make out on original image so I have used a few filters to highlight," he said in the video description. "What are these four objects? UFOs, Dust particles, or something else? As always you decide."

Experts say the four "objects" are actually just dead pixels in the rover's CCD camera — single points in the camera's imager that have lost functionality and register as white. Marc D'Antonio, a photo and video analyst for MUFON [Mutual UFO Network], told Huffington Post, "I fully concur at this point that these are dead pixels on the imager. All CCD [cameras] have them, and in a bland atmosphere like that at Mars, they would be very obvious as opposed to an active atmosphere like Earth, where they could end up hidden for a long time before anyone noticed them."

Photoshop filtering processes often blend, color-correct or contrast-heighten images in ways that turn single dead pixels into larger, more prominent shapes. In other words, "using a few filters" is exactly what the YouTube user should not have done in trying to clarify the contents of the Curiosity photo.